1. Field of the Invention
This invention relates to an image pickup apparatus having an image pickup element for converting an optical image to a plurality of color signals which are produced at an output thereof.
2. Description of the Related Art
In the image pickup apparatus receptive of an optical image for producing electrical signals for three primary colors, there is need to adjust the gain of the amplifier in the photoelectric converter circuit of each color system (or the so-called "white balance").
Conventionally, that this adjustment of the white balance is made to stationary light is the usual condition. Meanwhile, for the case of using a flash device, the only adjustment that is available is that the white balance is unequivocally determined in accordance with the color temperature of the light emitted from the flash device.
However, in photography using the flash device, situations in which as the environmental condition of an object to be photographed, the contribution from the stationary light (ambient light) cannot be ignored are not few.
In that case, by the adjustment of the white balance in accordance with only one of the ambient light and the flash light emitted as in the prior art, satisfactory photographs cannot be made.
In principle, this adjustment of the white balance is established with respect to a single light source within a certain category. Therefore, as illumination is made with two or more light sources of utterly different color temperature, when all of their contributions are not negligible, it is substantially impossible to adjust the white balance. This is the same even in the case that an illumination light source for photography is used as the presence of ambient light.
Thus, for the case that an image is picked up by using the illumination light source for photography, if the condition is such that there is a great disparity between the color temperatures of the illumination light for photography and the ambient light and moreover that both cannot be ignored in respect to each other, it results that the white balance adjustment becomes substantially impossible to perform. Also, even in the case that the ambient light had a plurality of color temperatures as with cocktail lights under the condition that the illumination light source was not used, the white balance adjustment could not be made.